WASHINGTON — Democrats’ high hopes of mitigating House losses in a rough election year have been dashed by reality.

The question now is not whether Republicans hold the House — that’s a given. Rather, it’s how many seats could the GOP add to its majority on Election Day? And how close could it get to its post-World War II high of 246 in Harry S. Truman’s administration?

Three weeks to Nov. 4, the House outlook remains bright for the GOP as national Democrats bail on once-promising opportunities in Virginia and Colorado, canceling television advertising to shift money to efforts to save vulnerable incumbents in Democratic-leaning states such as California and Illinois. Democrats also are transferring some of the cash to races where they stand a better chance.

President Barack Obama’s dismal approval ratings and midterm malaise have been a drag on Democrats, but the situation grew bleaker as Republican-leaning outside groups such as American Crossroads and American Action Network started pumping in millions of dollars targeting Democratic lawmakers.

Democrats cut $2.8 million in spending in northern Virginia, where John Foust faces state Del. Barbara Comstock in a seat that Republican Frank Wolf has held for 34 years. The party also scaled back its spending in the Denver suburbs by $1.4 million despite its high expectations that former state House speaker Andrew Romanoff could upend three-term Republican Rep. Mike Coffman in a district with a growing Hispanic population.