President Trump Donald John TrumpBiden says voters should choose who nominates Supreme Court justice Trump, Biden will not shake hands at first debate due to COVID-19 Pelosi: Trump Supreme Court pick 'threatens' Affordable Care Act MORE on Monday expressed support for Sen. Susan Collins Susan Margaret CollinsSenate GOP set to vote on Trump's Supreme Court pick before election Democratic senator to party: 'A little message discipline wouldn't kill us' Poll: 57 percent of Americans think next president, Senate should fill Ginsburg vacancy MORE (R-Maine) as she faces a contentious Senate race next year.

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Trump tweeted "I agree 100%" in response to a tweet from Sen. Lindsey Graham Lindsey Olin GrahamHarris slams Trump's Supreme Court pick as an attempt to 'destroy the Affordable Care Act' Sunday shows preview: Lawmakers prepare for SCOTUS confirmation hearings before election Confirmation hearing for Trump's Supreme Court pick to start Oct. 12 MORE (R-S.C.) that praised Collins.

"My friend @SenSusanCollins showed unbelievable courage during Justice Kavanaugh's confirmation and at other times when our country has needed a steady voice," Graham wrote last week.

"We need her to ensure a GOP majority in 2020. Please support her today," he added, including a link to the Collins campaign's donation page.

Collins last week officially announced her reelection bid in Maine, a state that Democratic presidential nominee Hillary Clinton Hillary Diane Rodham ClintonThe Memo: Trump furor stokes fears of unrest Bloomberg rolls out M ad buy to boost Biden in Florida Hillicon Valley: Productivity, fatigue, cybersecurity emerge as top concerns amid pandemic | Facebook critics launch alternative oversight board | Google to temporarily bar election ads after polls close MORE won in 2016.

The senator has been a key swing vote on several issues and was one of three Republicans who voted to uphold the Affordable Care Act. However, she voted with her fellow Republicans in favor of Brett Kavanaugh Brett Michael KavanaughSenate GOP set to vote on Trump's Supreme Court pick before election Conservative groups unleash ad blitz in support of Barrett's nomination Two Judiciary Democrats say they will not meet with Trump's Supreme Court pick MORE's controversial Supreme Court confirmation, drawing ire from some on the left.

She faces reelection next year in a race that the Cook Political Report has rated as a "toss-up."