Image copyright Getty Images Image caption Donald Trump waves goodbye to a crowd in Iowa, as well as to his impeachment trial

Donald Trump has been cleared by senators after his impeachment trial. How might his acquittal shape the 2020 race for the White House?

Both sides are now sifting through the political rubble just nine months before a national election that has the entire House, more than a third of the Senate, and the presidency itself on the ballot.

According to polls, the nation's political disposition is much as it was before the impeachment process began. The US is sharply divided along partisan lines. The president's approval ratings hover in the low to mid-40s, roughly where they've been the entirety of his term in office. His re-election chances are dicey but far from slim.

The decision not to seek witnesses - which polls show Americans overwhelmingly wanted - may be forgotten before long. After all, Democrats and Republicans had very different views about what "witnesses" means. The former wanted to hear from Trump administration officials like John Bolton and Mick Mulvaney, who they think could corroborate the charges against the president. The latter sought to call Joe Biden's son Hunter, head impeachment manager Adam Schiff and the whistleblower - and will be just as happy to see the whole matter put to rest.

Impeachment didn't change the existing political disposition in the US; instead, it was subsumed by it.

Polls don't tell the whole story, however, and there are other signs that the impeachment proceedings have made an impact.

A Republican base energised

At a rally in Des Moines, Iowa, on Thursday night, a basketball arena packed with supporters watched Trump once again rail against what he called the impeachment "hoax". He said that past impeachments proceedings - of Andrew Johnson in 1868, Richard Nixon in 1973 and Bill Clinton in 1999 - were "dark periods" in US history, but his presidency was a "happy" one.

The cheering crowd seemed to agree.

"I think he gets re-elected because of what Democrats are doing," said Tracy Root of Des Moines, who came to the rally with his son, Tony. "They couldn't beat him at the polls, so they've got to impeach him."

Sara Johnson, who drove four hours from Minnesota to attend the rally, said she had watched every minute of the trial and found Democratic efforts to convict the president "amusing".

If anything, she added, Trump was better off because Americans were seeing "how corrupt the system is".

Video caption Republicans don't want witnesses called in Trump's Senate trial. Here's why.

The political strategy for the White House at this point is clear: to paint impeachment as just another example of a Washington establishment that has been out to get the president - and, by connection, those who support him - from the beginning.

" They're not after me, they're after you ," Trump wrote in a December tweet. "I'm just in the way."

If Trump's campaign blueprint is to rally the base to support him in November - "the largest grass-roots campaign in US history", in the words of campaign manager Brad Parscale - the accusation by House Democrats and subsequent exoneration by Senate Republicans will be music to Republican ears.

A Democratic base reflective

In the months leading up to the start of the House impeachment investigation, a big question for Democrats was whether continued resistance to the move by the chamber's leadership - including Speaker Nancy Pelosi and Intelligence Committee chairman Adam Schiff - risked dispiriting their base voters who wanted to take the fight to the president.

In the end, those restive Democrats got the impeachment they wanted - a black mark on his presidency - if not the result they hoped for.

Massachusetts Senator Elizabeth Warren was one of the first major Democratic presidential candidates to call for Trump's impeachment. At an organising event for her supporters in Des Moines on Friday night, many were already looking ahead to November.

"The election is going to divide our nation again, but hopefully being truth-seekers will help Democrats come out on top," said Rachel Smith, a teacher from Urbandale, Iowa. "Other people who are more moderate and their decisions were not necessarily made up, this might swing them toward the Democrats."

Who will take on Trump in 2020?

Her husband, Justin, said that despite the outcome, he was glad the House had decided to impeach - and that a full airing of the president's alleged misdeeds was worth the effort.

"It was necessary to send a message that a line had been crossed," he said, adding that he wasn't in favour of impeachment until Trump's Ukrainian efforts came into public view.

At least for now, they agreed, they and their fellow Democrats would have to be satisfied with this outcome.

Biden damaged?

There is no evidence indicating that Biden engaged in any kind of misconduct in Ukraine, but in politics such technicalities don't always matter. True or not, if it hurts, it hurts.

And during the opening arguments for the president's defence team, former Florida Attorney General Pam Bondi did her best to make it hurt.

In her remarks, she sounded more like a prosecutor - laying out what she saw as the case against Hunter Biden and, by connection, his father, former Vice-President Joe Biden.

She said the Ukrainian energy company Burisma gave a board position to the Biden son in an attempt to influence US policy. She questioned whether Joe Biden did anything as point-man for the Obama administration's Ukraine policy that may have helped protect his son from investigation. That suspicion alone, she continued, should justify the president's decision to ask the Ukrainian government to look into the Bidens.

"All we are saying is that there was a basis to talk about this, to raise this issue, and that is enough," she said.

The impeachment investigation itself - and Biden's ties to it - may also be enough to adversely affect Biden's presidential campaign, even if Trump's attempt to get Ukraine to launch an investigation ultimately failed.

After Bondi's presentation, Iowa Republican Senator Joni Ernst was practically giddy as she suggested to reporters that Biden's presidential ambitions may have taken a hit.

"I'm really interested to see how this discussion today informs and influences the Iowa caucus voters, those Democratic caucus-goers," she said. "Will they be supporting Vice-President Biden at this point? Not certain about that."

Not all the results from Iowa are in yet, but Biden is currently languishing in a disappointing fourth place.

He has tried to turn Republican interest in damaging his political prospects into a strength, tweeting last week that Ernst and Trump are "scared to death I'll be the nominee" .

An October poll, however, showed that 40% of Democrats and most Republicans and independents think Hunter Biden's Ukraine dealings are a valid campaign issue .

In a Democratic nomination contest that is close, as will be the general election in the autumn, even a shadow of doubt could tilt the scales.

Holding the line

Perhaps the biggest tell about how this may shake out for the 2020 presidential campaign is to look at the handful of Republican senators facing tough re-election battles in November. When push came to shove, every single one of them did vote with the president.

There was some speculation that Republicans like Cory Gardner of Colorado, Martha McSally of Arizona or Susan Collins of Maine might break ranks, calculating that the political damage sustained from voting to exonerate the president in Democratic-leaning or closely divided states would be too great. Two of those three didn't even vote for new witnesses.

Mitt Romney, who is not up for re-election in Utah this year, was the only Republican to turn on the president. He voted to convict him on the first charge of abuse of power.

Video caption Trump 'guilty of an appalling abuse of public trust' - Mitt Romney

On the flip side, Democrat Doug Jones of Alabama - who may be the most at-risk senator on the ballot later this year - voted to convict.

If politicians with their professional livelihoods on the line did not break ranks, it may be because they know nothing has changed. In a sharply divided nation, the risk of angering the party faithful outweighs everything.

Never the end

Trump's Senate impeachment trial may have drawn to its seemingly foregone conclusion, but the end of one chapter won't close the book on the president's Ukraine-related headaches.

Even though former National Security Advisor John Bolton will not be asked to testify before the Senate, his account of how the president pressured Ukraine to open up Biden investigations is just starting to come out. It could be fully revealed if his upcoming memoir is published or if he chooses to talk publicly. House Democrats have said they could even try to call him as a witness, perhaps triggering the kind of gruelling court fight they bypassed the first time around.

The House could decide to bring in others to testify, such as former Trump chief of staff John Kelly, who has recently made statements supporting Bolton's assertions. In fact, according to columnist Jonathan Alter, witnesses after the trial concludes might end up being more helpful to Democrats.

"When Bolton testifies in the House," Mr Alter writes, "it'll be a major event, not one overrun by an acquittal, as would have happened had he testified in the Senate. Trump's scheme will be in the news all the way to Labor Day ."

That may end up being wishful thinking, but if history is any guide, there's no telling where or when the next revelation could come. This unknown may be more than enough to cause heartburn for Trump and Republicans.

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