President Barack Obama’s “if you like it, you can keep it” promise has House Democrats facing a dilemma as they look ahead to a vote on Republican legislation to preserve existing health plans. “There will be defections,” a House Democratic leadership aide predicted. The bill, sponsored by House Energy and Commerce Chairman Fred Upton, R-Mich., would give insurance companies the option of continuing all existing health plans for a year. It’s considerably weaker than a proposal by Sen. Mary L. Landrieu, D-La., that would require insurance companies to continue offering existing plans, but the political power of the legislation may...