<p class="ingestion featured-caption">Sens. Lisa Murkowski, Bill Cassidy, Susan Collins, and Mitt Romney are among the Republican senators who haven't endorsed Trump.Drew Angerer/Getty Images</p><ul class="summary-list"><li>Several GOP senators have not endorsed Trump — and likely won't before the election.</li><li>Some of them voted to impeach Trump after January 6 and have sworn him off entirely.</li></ul><p>With the 2024 presidential election just around the corner, a solid chunk of the Senate Republican conference still won't get behind former President Donald Trump.</p><p>He's not alone in failing to lock up the formal support of the entire group. Four members of the Senate Democratic caucus also haven't endorsed Vice President Kamala Harris, including three of the four independents who caucus with Democrats — Sens. Angus King of Maine, Joe Manchin of West Virginia, and Kyrsten Sinema of Arizona. </p><p>Democratic Sen. Jon Tester has also opted to remain neutral, he has said, in order to remain focused on his <a target="_blank" class href="https://www.businessinsider.com/us-senate-races-2024-election-landscape-democrats-republicans-2023-1">tough reelection fight</a> in Montana.</p><p>But Trump's lack of support among some Republican senators is notable, given that many of the holdouts condemned him in strong terms since he attempted to overturn the results of the 2020 election. </p><p>In fact, four of the senators who haven't endorsed Trump were among the <a target="_blank" class href="https://www.businessinsider.com/gop-senators-voted-to-convict-trump-facing-backlash-from-republicans-2021-2">original 7 Republicans</a> who voted to convict Trump after the January 6 insurrection.</p><p>Here's a closer look at each Republican senator who has declined to endorse Trump — and why.</p>