President Barack Obama issued a final passionate plea to voters on Tuesday

President Barack Obama issued a final passionate plea to voters on Tuesday to bridge the divide in American politics after he leaves office.

In his last State of the Union address delivered to a Congress that has often hobbled his ambitions, Obama expressed regret over his own role in Washington's political dysfunction, and lambasted Republican presidential candidates who he said are adding to the trouble.

He also offered his pitch to fix it -- including structural reforms to a political system he said even those in Washington don't like.

Here are five takeaways from Obama's speech:

Obama's lament

He was the candidate of transformational change -- and then the president who led during an era of shutdowns, dysfunction and the erosion of the political center.

Obama admitted his disappointment.

"It's one of the few regrets of my presidency  --  that the rancor and suspicion between the parties has gotten worse instead of better," Obama said. "There's no doubt a president with the gifts of Lincoln or Roosevelt might have better bridged the divide, and I guarantee I'll keep trying to be better so long as I hold this office."

He offered a prescription, saying it's about the process, not the people who are elected.

Obama pitched the removal of legislatures from redistricting; a reduction of the influence of money in politics; and laws that make it easier to vote.

He also admitted that accomplishing those reforms is harder than the idealism that put him on the national political map might suggest.

"What I'm asking for is hard. It's easier to be cynical; to accept that change isn't possible, and politics is hopeless, and to believe that our voices and actions don't matter," Obama said.

He added: "As frustration grows, there will be voices urging us to fall back into tribes, to scapegoat fellow citizens who don't look like us, or pray like us, or vote like we do, or share the same background. We can't afford to go down that path. It won't deliver the economy we want, or the security we want, but most of all, it contradicts everything that makes us the envy of the world."

On this topic, South Carolina Gov. Nikki Haley, who rebutted Obama's address. offered some support for the President.

"Often the best thing we can do is turn down the volume. When the sound is quieter, you can actually hear what someone else is saying," she said. "And that can make a world of difference."

Obama's Trump rebuttal

Obama denounced "political hot air." He said politicians who say the economy is sagging are "peddling fiction." He declared the United States "the most powerful nation on Earth. Period. It's not even close."

And if there was any remaining doubt he was talking about Donald Trump, Obama got even more specific.

"We need to reject any politics that targets people because of race or religion," Obama said in a not-very-veiled reference to Trump's proposal to ban all Muslims from entering the United States.

"This isn't a matter of political correctness. It's a matter of understanding what makes us strong," Obama said. "The world respects us not just for our arsenal; it respects us for our diversity and our openness and the way we respect every faith."

Obama wasn't the only one who bashed Trump, though.

Haley -- tapped by House Speaker Paul Ryan and Senate Majority Leader Mitch McConnell unloaded on the man who's leading the polls in her state's crucial Republican presidential primary.

"During anxious times, it can be tempting to follow the siren call of the angriest voices," Haley said. "We must resist that temptation. No one who is willing to work hard, abide by our laws, and love our traditions should ever feel unwelcome in this country."

Obama took a swing at other GOP candidates, too -- particularly Texas Sen. Ted Cruz, who has said he wants to carpet bomb ISIS to "see if sand glows in the dark."

Obama said: "The world will look to us to help solve these problems, and our answer needs to be more than tough talk or calls to carpet bomb civilians. That may work as a TV sound bite, but it doesn't pass muster on the world stage."

Obama the preacher

The moments Obama's supporters will most remember long after he's left office have been aspirational: His "red states" and "blue states" speech at the 2004 Democratic National Convention; his singing of "Amazing Grace" after the church shooting in Charleston, South Carolina.

Obama offered another on Tuesday night, harnessing his oratorical skills to call on Americans to put to use what Martin Luther King, Jr. called "voices of unarmed truth and unconditional love."

"I see it in the American who served his time, and dreams of starting over  --  and the business owner who gives him that second chance. The protester determined to prove that justice matters, and the young cop walking the beat, treating everybody with respect, doing the brave, quiet work of keeping us safe," Obama said.

"I see it in the soldier who gives almost everything to save his brothers, the nurse who tends to him 'til he can run a marathon, and the community that lines up to cheer him on.

"It's the son who finds the courage to come out as who he is, and the father whose love for that son overrides everything he's been taught.

"I see it in the elderly woman who will wait in line to cast her vote as long as she has to; the new citizen who casts his for the first time; the volunteers at the polls who believe every vote should count, because each of them in different ways know how much that precious right is worth."

Moonshot Joe

When he announced he wouldn't run for president, Vice President Joe Biden said he wants to see a "moonshot" to cure cancer in the United States.

Obama said he wants to give it to Biden -- whose son Beau, Delaware's attorney general, died of brain cancer last year -- and put his vice president "in charge of mission control."

"Last year, Vice President Biden said that with a new moonshot, America can cure cancer. Last month, he worked with this Congress to give scientists at the National Institutes of Health the strongest resources they've had in over a decade," Obama said.

"Tonight, I'm announcing a new national effort to get it done," he said. "And because he's gone to the mat for all of us, on so many issues over the past forty years, I'm putting Joe in charge of Mission Control. For the loved ones we've all lost, for the family we can still save, let's make America the country that cures cancer once and for all."

It was perhaps the only Obama policy pitch that drew strong applause from both sides of the aisle.

The cheers and smiles from Republican senators underscored the vice president's popularity on Capitol Hill, where he spent most of his adult life. It demonstrated why Biden has been able to do what Obama couldn't, playing an instrumental role in negotiating legislative deals with Congress to avert shutdowns and fund the government.

Ryan's stoicism

Americans accustomed to now-retired Speaker John Boehner's easy shows of emotion -- with tears flowing on many occasions -- might have been surprised to see the stone-cold expression on new Speaker Paul Ryan's face throughout Obama's speech.

Most of Ryan's words and gestures were toward Vice President Joe Biden, the man he debated on national television in 2012 when Ryan was Mitt Romney's choice as the Republican vice presidential candidate.

But he didn't react to Obama's policy talk -- nearly all of which was at odds with Ryan's priorities.

Obama did include an olive branch of sorts to Ryan, who recently apologized after characterizing the United States as full of "makers" and "takers." Ryan has said he hopes to address the issue of poverty while speaker.

"I also know Speaker Ryan has talked about his interest in tackling poverty. America is about giving everybody willing to work a hand up, and I'd welcome a serious discussion about strategies we can all support, like expanding tax cuts for low-income workers without kids," Obama said.