Democrats have a strategy for holding the U.S. Senate this year: Limit their losses to five seats or fewer, and then pick off Sen. Mitch McConnell, perhaps even swipe the GOP's open seat in Georgia. It won't be easy.
Three Republican nominees—Montana Rep. Steve Daines, former South Dakota Gov. Mike Rounds and West Virginia Rep. Shelley Moore Capito —lead by double-digits in the Real Clear Politics (RCP) average of recent polls. If the mid-July Federal Election Commission fundraising reports show these Republicans with healthy cash advantages, Democratic interest and money could go elsewhere.
That doesn't mean these Republicans will be home free. If Democrats sense an opportunity, they will jump in with last-minute attack ads. But with Montana, South Dakota and West Virginia probably not in the cards—half the seats Republicans need to win a majority—Democrats hope to save endangered incumbents elsewhere.
That could be tough. RCP shows Republican challengers, despite being less well-known, running ahead of Democratic senators in Louisiana and North Carolina, even in Alaska, and trailing in Arkansas by 1%.
So Democrats have ripped a page from the Obama campaign's 2012 playbook. The party spent lavishly to turn swing voters against Mitt Romney, and Democrats have now launched a similar summer offensive to hold these four Senate seats. The lines of attack differ, but the common thread is deception.
In North Carolina, Sen. Kay Hagan and outside groups have $1.9 million in ads already set to run between June and Sept. 1, while Emily's List and Planned Parenthood have pledged $6 million to defeat Republican State House Speaker Thom Tillis.
Emily's List is running spots saying Mr. Tillis "cut almost $500 million from education." Before Mr. Tillis became speaker in 2011, the North Carolina K-12 education budget was $7.15 billion. It's $7.81 billion this fiscal year and is expected to climb to $8 billion next year.
In Louisiana, Sen. Mary Landrieu and liberal interests have $1.4 million in summer ads accusing GOP Rep. Bill Cassidy of supporting "government-run health care." FactCheck.Org calls this "pure invention" and "audaciously false." Democrats don't care. By wrapping ObamaCare around Mr. Cassidy, they hope to help nominate a weaker GOP candidate against Mrs. Landrieu.
Alaska Sen. Mark Begich and a super-PAC funded by Senate Majority Leader Harry Reid have reserved $1.4 million in summer ad time so far. After failing to convince voters that Alaska's former attorney general and natural resources commissioner was not an Alaskan, they are now accusing Republican Dan Sullivan of limiting where Alaskans "can hunt and fish." That is false.
Arkansas Sen. Mark Pryor and liberal groups have bought $1.7 million of ads this summer to trash GOP Rep. Tom Cotton for supporting an increase in the Social Security retirement age. Mr. Pryor has been on record supporting this change since 2011.
Democrats want to make these Republicans toxic to voters inclined to replace lawmakers who rubber stamp the Obama agenda. If Republicans keep that from happening by Labor Day, they could take three or four of these red states.
GOP candidates must raise and deploy enough resources to combat this summer offensive, while counting on outside groups like American Crossroads (which I helped found) to keep pressure on these Democrats and their records.
Democratic troubles aren't limited to red states. Four other Democratic seats are already competitive. RCP says Republican state Sen. Joni Ernst is leading in Iowa and Republican Rep. Cory Gardner is down by less than 2% in Colorado. Former Secretary of State Terri Lynn Land in Michigan and former U.S. Sen. Scott Brown in New Hampshire are within 5%. The Democrats in these races are stuck around 44%, dangerous territory for incumbents. In Oregon, Minnesota and Virginia, Republican challengers trail by double digits but the incumbent Democrats can't break 50%, showing voters aren't sure they deserve re-election.
Democratic hopes of snatching Republicans seats aren't panning out so far. Senate Minority Leader McConnell continues running a disciplined campaign in Kentucky while his Democratic challenger, Alison Lundergan Grimes, stumbles over issues ranging from her party's war on coal to ObamaCare. In Georgia, Democratic candidate Michelle Nunn has gotten off to a shaky start while the GOP runoff is between two candidates both capable of winning the general election, Rep. Jack Kingston and businessman David Perdue.
The election is in November but key Senate races could be determined this summer. For Republicans to regain control of the Senate, surviving this early onslaught is critical.
A version of this article appeared June 19, 2014, in the U.S. edition of The Wall Street Journal, with the headline Democrats Try A Romney Redux Strategy and online at WSJ.com.