WASHINGTON — After countless dire emails and months of fading bravado, national Democrats in recent days have signaled with their money what they have been loath to acknowledge out loud: They will not win back the House and they will most likely lose additional seats in November.

Since last week, the Democratic Congressional Campaign Committee has essentially given up efforts to unseat Republicans in several races, pulling advertising money from a dozen campaigns in Republican-held districts to focus on protecting its embattled incumbents.

Democrats need 17 Republican seats to win back the majority, but of the 25 races still on the campaign committee’s battlefield, only seven currently belong to Republicans. That means Democrats are playing defense in 18 districts and offense in seven.

“This is shaping up to be the quintessential sixth year of a president’s term, and a referendum on this president,” said Representative Greg Walden of Oregon, chairman of the National Republican Congressional Committee, the campaign committee’s Republican counterpart.