FILE PHOTO: Senate Homeland Security and Governmental Affairs Committee ranking member Claire McCaskill (D-MO) questions Department of Homeland Security Secretary Kirstjen Nielsen during a Senate Homeland Security and Governmental Affairs Committee hearing on "Authorities and Resources Needed to Protect and Secure the United States," on Capitol Hill in Washington, DC, U.S., May 15, 2018. REUTERS/Erin Schaff/File Photo

WASHINGTON (Reuters) - Democratic U.S. Senator Claire McCaskill, facing a tough re-election battle in Missouri, said on Wednesday she will vote against confirming President Donald Trump’s nominee to the U.S. Supreme Court, Brett Kavanaugh.

In a statement posted on Twitter, McCaskill said her decision is not based on recent allegations that Kavanaugh, currently a federal judge, assaulted a girl in high school, which Kavanaugh denies. Instead, she said, she will vote against him because of “his positions on several key issues, most importantly the avalanche of dark, anonymous money that is crushing our democracy.”

Trump, a Republican, won Missouri in the 2016 presidential election.