In 2016, Donald Trump overwhelmed 16 qualified Republican primary rivals and became the first major-party presidential nominee without prior political or military experience. Against even greater odds, Trump defeated in the general election a far better funded and politically connected Hillary Clinton.

What are his chances of repeating that surprising victory in 2020?

In 2016, Trump had no record to run on. That blank slate fueled claims that such a political novice could not possibly succeed. It also added an element of mystery and excitement, with the possibility that an outsider could come into town to clean up the mess.

Trump now has a record, not just promises. Of course, his base supporters and furious opponents have widely different views of the Trump economy and foreign policy.

Yet many independents will see successes since 2017, even if some are turned off by Trump's tweets. Still, if things at home and abroad stay about the same or improve, without a war or recession, Trump will likely win enough swing states to repeat his 2016 Electoral College victory.

If, however, unemployment spikes, inflation returns or we get into a war, he may not.

At about the same time in their respective presidencies, Bill Clinton and Barack Obama had approval ratings similar to Trump's. In Clinton's first midterms, Democrats lost 14 more House seats than Republicans lost last November. Democrats under Obama lost 23 more seats in his first midterms than Republicans lost under Trump. Democrats lost eight Senate seats in 1994 during Clinton's first term. They lost six Senate seats in 2010 during Obama's first term. Republicans actually picked up two Senate seats last fall.

Yet Clinton and Obama handily won re-election over, respectively, Bob Dole and Mitt Romney. In other words, the 2020 election is likely Trump's to win or lose.

It's also worth remembering that Trump does not exist in a vacuum. In 2016, many voters preferred Trump because he was not the unpopular Hillary Clinton.

In 2020, there will be an even starker choice. Trump, now an incumbent, will likely run on the premise that he is the only thing standing between voters and socialism.

The power of that warning will depend on whether the Democrats continue their present hard-left trajectory or the eventual Democratic nominee manages to avoid getting tagged with what are as of now extreme progressive talking points.

The Green New Deal, a wealth tax, a top marginal income tax rate of 70 percent, the abolition of ICE, the abolition of the Electoral College, reparations, legal infanticide as abortion, the cancellation of student debt, free college tuition, Medicare for all and the banning of private insurance plans are not winning, 51 percent issues.

If the Democratic nominee embraces most of these fringe advocacies -- or is forced by the hard left to run on some of them -- he or she will lose. If the Democrats nominate Sen. Kamala Harris, Sen. Elizabeth Warren, Sen. Bernie Sanders or Sen. Cory Booker, Trump will seem moderate by comparison and have more relative experience at both presidential campaigning and governance.

Also, with a few notable exceptions such as John F. Kennedy and Barack Obama, senators do not have a good record of winning the presidency.

If the Democrats nominate a veteran politician such as former Vice President Joe Biden, then the two rivals will be more equally matched in appealing to the middle classes.

Another thing to consider: What will the Mueller investigation and a flurry of House investigations of Trump look like by November 2020?

If special counsel Robert Mueller concludes that there was no collusion between the Trump campaign and Russia, then Trump's charges of a "witch hunt" will more than likely stick. But if Mueller's investigation proves that Trump negotiated with the Russians to stop the Clinton campaign, Trump will be in considerable trouble.

At some point, all the progressive obsessions to abort the Trump administration -- the efforts to warp the voting of the Electoral College electors; to invoke the 25th Amendment, the Logan Act and the emoluments clause; and to thwart Trump from the inside, as former FBI Deputy Director Andrew McCabe and the anonymous New York Times editorialist have detailed -- have to show results.

If they do not by 2020, then these attempts will be seen more as bitter-end vendettas. And they may work in Trump's favor, making him appear a victim of an unprecedented and extraconstitutional assault. Then, in Nietzschean terms, anything that did not end Trump will only have made him stronger.

Finally, Trump himself is not static.

For a while, relative calm has returned to the White House. Secretary of State Mike Pompeo, national security adviser John Bolton and Attorney General William Barr are more in sync with Trump's style and message than the previous holders of those positions.

Trump himself often displays more self-deprecation. Like other incumbents, Trump may be becoming savvier about the complexities of the job.

Democrats think 2020 will be an easy win over a controversial and often wounded president. Republicans thought the same thing in 2012.

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