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Back in January, Democrats confidently predicted a "blue wave" would wipe out Republican control of Congress in this year's midterms -- as polls showed a massive lead for the party in the so-called generic ballot. 

This forecast is looking less certain as that lead shrinks by the week, with one poll even showing Republicans on top.

The "generic" ballot asks voters which party they plan to support, without getting into specific candidates. As recently as April, a Reuters poll showed Democrats with a 13-point lead. Some Democrats cited various surveys, including a CNN poll in December that showed an 18-point lead, as proof that they'd at least claim the House in November.

“#Megatsunami next November,” predicted an excited Rep. Ted Lieu, D-Calif.

But that lead has all but disappeared, with Reuters' latest poll showing a slight Republican edge of less than 2 percent. The trend is reflected in other polls. A CNN poll this month showed the Democratic lead at just 3 percent, down from 16 percent in February.

However, other polls have showed that Democrats still have a strong lead, with a Monmouth University poll this month giving Democrats a solid eight-point lead. The RealClearPolitics average of the ballot polls has shown the race tightening, but still gives them a 3.4 percent edge.

The change in attitude comes as the economy continues to do well and as Democratic leaders struggle to corral their members into focusing on a message that goes beyond anti-Trump rhetoric and Russia.

The results of recent primaries where liberal candidates beat moderate rivals have also changed the general election landscape. Fox News' Power Rankings updated ratings this week to reflect a Republican advantage in several races.

FOX NEWS POWER RANKINGS: DEM DIVIDES EMERGE

House Democratic Leader Nancy Pelosi, for her part, has urged the liberal flank of her party to move away from impeachment talk and focus instead on economic issues that affect everyday Americans -- a move that has led to backlash from some quarters.

“It comes down to an economic message,” Pelosi said in an interview this month. “The financial instability of American families is something that needs to be addressed."

DEM REP RIPS PELOSI FOR UNDERMINING TRUMP IMPEACHMENT PUSH

Pelosi also said this month that she would work to roll back the Trump tax cuts if they retake Congress, a statement Republicans have cited as proof that Democrats want to raise taxes.

"Now you’ve heard it straight from Nancy Pelosi’s mouth: if Democrats take back the House and she’s reinstalled as Speaker, your taxes will go up," a National Republican Congressional Committee spokesman said in a statement.

On Monday, the Democrats unveiled a plan to highlight alleged corruption in the Trump administration.

FULL MIDTERM COVERAGE

“Instead of delivering on his promise to drain the swamp, President Trump has become the swamp,” Pelosi said, according to The Washington Post.

But as Democrats try to sharpen their message, leaders also have to deal with a brewing civil war.

Pollster and Fox News contributor Doug Schoen pointed to Tuesday’s primary contests that he says show how progressives are overwhelmingly beating more moderate primary opponents.

A CIVIL WAR IS LOOMING FOR DEMOCRATS. PRIMARY RESULTS TUESDAY IN FOUR STATES EXPLAIN WHY

“Overall, Tuesday’s results prove that the problematic trend of far-left progressives winning Democratic primaries over moderate centrists continues, showing that the party is more divided than ever,” he wrote. “It is time to move forward with a plan that unifies, rather than divides the party, or squander the opportunity to retake either chamber of Congress in November.”

In the meantime, Rep. Lieu -- who predicted the megatsumani in December -- is taking a different approach, and is now downplaying the generic ballot as a means to forecast the November race.

“Do folks still think the national generic ballot means anything?" he asked. “It’s the individual districts that matter. And in those districts, Democrats are crushing it.”