The nonpartisan election forecaster Sabato’s Crystal Ball shifted its rating of the Colorado Senate race to “leans Democratic” from a “toss-up” on Thursday.

The rating switch comes as recent polling has shown Colorado voters are more disapproving of Sen. Cory Gardner Cory Scott GardnerSenate Republicans face tough decision on replacing Ginsburg What Senate Republicans have said about election-year Supreme Court vacancies Chamber of Commerce endorses McSally for reelection MORE (R-Colo.) than they are of President Trump Donald John TrumpObama calls on Senate not to fill Ginsburg's vacancy until after election Planned Parenthood: 'The fate of our rights' depends on Ginsburg replacement Progressive group to spend M in ad campaign on Supreme Court vacancy MORE.

Sabato’s Crystal Ball cited polling in the state, noting polls in Colorado have been sparse and that the GOP senator is in a tough spot, risking losing some of his own base voters if he criticizes Trump.

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Just 37 percent of Colorado voters approve of Gardner, and 48 percent said they disapprove of him, according to a poll from Global Strategy Group conducted between Jan. 31 and Feb. 4.

The same poll found 44 percent of Colorado voters approve of Trump and 56 percent disapprove of the president.

Trump’s approval was also stronger than Gardner's among “very conservative” and “not very conservative” Republicans, though both men had the overwhelming support from this group, according to the poll which surveyed 818 registered voters.

Only 1 percent of “very conservative” Republicans disapprove of Trump, but 16 percent of those "very conservative" Republicans said they disapprove of the senator.

The poll was conducted by a combination of text-to-web methodology with voters chosen at random from the voter file and respondents recruited from opt-in online vendors.

Colorado is one of several Senate seats Democrats are looking to flip in November in an attempt to win control of the upper chamber.

Democrats will choose a nominee in a March 3 primary. Among those running is former Colorado Gov. John Hickenlooper John HickenlooperGOP campaign director: 'There's no doubt that Republicans will control the Senate' Susan Collins challenger open to nixing Senate filibuster Democrats struggle to harness enthusiasm of Gen Z voters MORE who announced his Senate bid after ending his short-lived presidential campaign.