Anyone who runs for president has to confront their past. Not only do they have to worry about misdeeds that might come to light when teams of opposition researchers and media busybodies start poking around, they may also have to adjust their ideological profile to match the party they’re trying to represent. It can a problem of both geography and time, and it’s one that multiple Democrats seeking to run against Donald Trump in 2020 are facing. That always makes for uncomfortable questions, but I’m going to argue that it isn’t something voters should worry too much about.

To see what I mean when I say it’s a problem of geography and time, let’s take the example of Sen. Kirsten Gillibrand (D-N.Y.), who announced her presidential candidacy last week. When she began her career in the House, Gillibrand represented a conservative district in Upstate New York and had positions to match it, including being pro-gun and rather harsh when it came to undocumented immigrants. Then 10 years ago she was appointed to fill Hillary Clinton’s Senate seat and found herself representing a state that in its entirety is much more liberal than her district was. And now she’s running to represent the entire Democratic Party, which is fairly similar to her New York constituents, but even over just that decade has moved left, especially on immigration.

On CNN’s “State of the Union” Sunday, Jake Tapper asked Gillibrand about mailers her campaign sent out in 2008 when she was running for reelection to her House seat, opposing amnesty for “illegal aliens” and advocating making English the official language of the United States. Here’s how she replied:

TAPPER: But, let me ask you, if Trump's immigration positions are racist, were they racist when you held some of those positions as well? 
GILLIBRAND: They certainly weren't empathetic, and they weren't kind, and I did not think about suffering in other people's lives. 
And one thing I did 10 years ago, when I became senator and was going to represent 20 million people across our state, I recognized that a lot of places in my state were different, and I needed to understand what those constituents needed too. And so I took the time. 
I went down to Brooklyn. I met with [Rep.] Nydia Velázquez, who has been a leader fighting for families for a long time. And I listened. And I realized that things I had said were wrong. I was not caring about others. I was not fighting for other people’s kids, the same way I was fighting for my own. And I was wrong to feel that way.

She tells a similar story about her other major shift, on guns: In 2009 she met with the parents of a teenager killed by a stray bullet, and the meeting was so powerful that she reevaluated everything she had thought on the subject.

Whether you accept these kinds of epiphany stories will depend almost entirely on how you already feel about the politician in question. For instance, President Trump explained his evolution from pro-choice to pro-life by saying that “what happened is friends of mine years ago were going to have a child, and it was going to be aborted. And it wasn’t aborted. And that child today is a total superstar, a great, great child. And I saw that.” Coming from Trump, that story is almost impossible to believe. But Republicans would ask, “Who cares?” As on many issues, once he moved to where his party was, he has to come through for them.

Which is exactly how it usually goes. The candidate takes the new position and tells a (sometimes marginally) plausible story about why they changed their minds; then if they actually take office, not only will they not go back to their old position, they’ll be under extra pressure to reassure their party that they are reliable. It’s the inverse of the only-Nixon-could-go-to-China idea: Since their bona fides are already suspect, they have no room to buck their party on that issue.

Gillibrand’s situation of starting in a place that isn’t representative of her party and then having to change as she moves to the national stage has plenty of precedents. But the evolution over time may be more common, especially in the past couple of decades as the parties have grown steadily more ideologically more homogeneous and shifted away from the center.

For instance, when Clinton joined her husband in the White House in 1993, it was standard for a Democrat to oppose same-sex marriage and support “tough on crime” measures; she had to apologize for both when she ran for president in 2016. By then Democratic tolerance for dissent from the party’s position on guns had narrowed, which left Bernie Sanders explaining that his sometimes pro-gun record was because Vermont is a rural state where lots of people have guns. In other words, he was faithfully representing the beliefs of his constituents, which you can either say is what a representative should do or is just pandering.

Other Democratic candidates are going to confront this issue as the primaries proceed. Rep. Tulsi Gabbard has already released a video apologizing for her previous opposition to marriage equality. Sen. Kamala D. Harris will be criticized for some of her actions as a prosecutor in California. Former vice president Joe Biden will be grilled on his authorship of the harsh 1994 crime bill (among other things). Sen. Cory Booker will have to defend prior ties to Wall Street. Retired boxer Oscar De La Hoya will have to explain his long record of punching other men in the face (though you probably didn’t know, he’s thinking of running, too).

They’ll all probably say that they’re different today than they were then, and while voters will inevitably judge their sincerity, you don’t really have to believe a politician is sincere when they make this move. Why? Because once they shift, they seldom go back. They don’t get elected and then say, “Ha ha, I fooled you all!” As a voter, you’d do better to accept the change and judge them on whether you like the positions they take now. Because that’s almost certainly what they’ll do if they become president.