This article discusses whether candidates and campaigns in US House elections condition the influence of national political tides by magnifying their effects at the local level. Using election returns, it is shown that this interaction effect is quite small: a positive national tide increases votes for weak candidates almost as much as strong ones. However, competition and national tides in US House elections do interact to produce turnover: high-spending challengers rarely win without the help of a national tide. Contrary to many accounts in the American politics literature, it is also found that the tide's influence is weaker in open seats in certain important ways. Together, these findings suggest that US House candidates benefit from national tides but have a limited ability to create them, and that the prospects for national responsiveness are hurt by the trend towards heavier competition in open seats.