U.S. Sen. Elizabeth Warren appears headed for a costly re-election victory, one in which even her own supporters are rejecting her national ambitions and still expressing doubts about her claims of Cherokee ancestry.

Warren holds a comfortable 20-point lead over GOP opponent Geoff Diehl heading into Tuesday’s election, but landing just a few points above 50 percent is not especially impressive in a state where Democrats outnumber Republicans by a 3-1 margin.

Warren was hoping for a rousing mandate from voters to propel her into her next step — a run for the White House. But her unpopularity in Massachusetts actually appears to be ticking up a bit. Nearly four in 10 voters have an unfavorable view of the Cambridge Democrat, according to the latest Suffolk University poll.

That’s a troubling number for a Democrat in one of the bluest states in the nation, and indicates what a polarizing figure Warren has become, even in her own backyard.

On the stump, Diehl has dinged up Warren, slamming her on a daily basis for focusing more on her presidential run than her constituents. And she now faces an ethics complaint over charges that she raised funds off of her vote to try to block Justice Brett Kavanaugh.

But most importantly, a whopping two thirds of all Massachusetts voters don’t want her to run for president — a number that can’t be going over well in Warren’s 2020 war room.

If voters in the Bay State, where Warren is headed for re-election, reject her planned White House run, what will voters in the rest of the nation think?

And a significant number of voters, especially men, continue to say that Warren hasn’t put to rest questions about her listing herself as Native American in a national law school guide.

Warren’s much-hyped DNA test, intended to dispel doubts about her heritage, instead made it look like she was desperately trying to cling to her past claims of minority status.

All the test confirmed was that at most Warren has minuscule strands of Native American DNA — about the same as millions of other Americans.

In the Suffolk poll, just 52 percent of women and 40 percent of men said the test put to rest questions about her heritage — not exactly the overwhelming show of support she was looking for.

And don’t forget — that’s in liberal Massachusetts. The doubts about her Indian ancestry would probably be greater across the rest of the nation, where Democrats and Republicans are more evenly split.

Warren’s re-election campaign also shows signs of wear and tear. While she hasn’t made a major stumble, she hasn’t dominated her debates with the Whitman state representative the way a veteran incumbent should.

All of this doesn’t bode well for a Warren White House run.