WASHINGTON — Republicans and liberal Democrats have something in common: Both are trying to keep alive the prospect that Massachusetts Sen. Elizabeth Warren will run for president.

Warren isn’t playing along, making the rounds this week to — yet again — insist she’s not interested in the White House.

People on both sides have a vested interest in clinging to a dream that is all but certain to remain in the realm of fantasy. The left flank of the Democratic Party wants Warren to challenge Hillary Rodham Clinton in the primary race, or at a minimum, get Clinton to adopt Warren’s tough-on-Wall Street agenda. Republicans view a Warren candidacy as a way to sow division among Democrats and boost their own fundraising.

Neither side seems to care much that Warren has repeatedly insisted that she doesn’t plan to run for president and is not taking any of the necessary steps to lay the groundwork. That has been the message as Warren conducts a media blitz this week surrounding the paperback release of her memoirs.