U.S. Vice President Kamala Harris' move to the top of the Democratic ticket has injected new life into her party's flailing presidential campaign against Republican former President Donald Trump, but some lawmakers whose support she will need if she wins are keeping her at arm's length.

In the 35 competitive races that will determine control of the 435-seat House of Representatives in the Nov. 5 election, 12 Democratic incumbents or challengers have so far held off on endorsing Harris.

They are presenting themselves as independent decision-makers focused on their constituents rather than national politics, distancing themselves from a candidate that Republicans tie to the Biden administration's record on immigration and inflation.