WASHINGTON — Hillary Clinton’s search for a running mate is moving into a more intense phase, according to several Democrats, as aides contact a pared-down pool of candidates to ask for reams of personal information and set up interviews with the presumptive Democratic nominee’s vetting team.

Those on the shortlist include Massachusetts Sen. Elizabeth Warren, a favorite of progressives who has emerged as a blistering critic of presumptive Republican nominee Donald Trump; Virginia Sen. Tim Kaine, a well-liked lawmaker from an important general election battleground state; and Housing and Urban Development Secretary Julian Castro of Texas, a rising star in the Democratic Party.

Vermont Sen. Bernie Sanders, Clinton’s toughest primary rival, is not on the shortlist of vice presidential candidates, according to one Democrat.

A small group of Clinton campaign confidants has been sifting through publicly available information about more than two dozen possible contenders for more than a month.