Democrats have a real shot at winning two of the three Senate seats where Republicans are most vulnerable in the midterm elections, according to a new Axios/SurveyMonkey poll.

The bottom line: The poll provides new evidence that Republicans' hold on the Senate may not be as solid as it once looked. Democrats could win the open Arizona seat and possibly defeat Republican incumbent Dean Heller in Nevada. The third race, in Tennessee, is a statistical tie.

Why it matters: Losing both the House and the Senate to Democrats would be a clear repudiation of President Trump and his brand of Republicanism, as Axios' Mike Allen writes. And Democrats have been clearly outperforming in the special elections since Trump became president.

Yes, but: The overall Senate map in this election still favors the GOP, and an earlier Axios/SurveyMonkey poll showed five Senate Democrats could lose their seats to Republicans. Democrats need to keep the Senate seats they have and gain two more to take control of the Senate.

DACA is the biggest warning sign for Republicans: 64% of voters across all three states support protections for immigrants brought illegally to the U.S. as children, and 71% support offering immigrants a chance to apply for citizenship rather than deporting them.

They won't get traction on health care, either: Roughly half of voters in all three states want to fix the Affordable Care Act "so it works better." Only about three in 10 want to repeal it.

Roughly half of voters in all three states want to fix the Affordable Care Act "so it works better." Only about three in 10 want to repeal it. One sign of hope for Republicans: Despite their vulnerability in these states, nearly half of all voters in the three states think the economy is better off today than it was a year ago.

Methodology: These SurveyMonkey/Axios online polls were conducted April 2- April 23, 2018 among a total sample of 1,667 registered voters living in Arizona, 1,332 registered voters living in Nevada, and 1,639 registered voters living in Tennessee. Respondents were selected from the nearly 3 million people who take surveys on the SurveyMonkey platform each day. The modeled error estimate is 4 percentage points for Arizona, 5 percentage points for Nevada, and 4 percentage points for Tennessee. Crosstabs available here.