(CNN) Everything seems to be going the Democrats' way on their march for House control in November. Republicans, including House Speaker Paul Ryan, are retiring left and right. Democrats continue to overperform in special elections. Nonpartisan handicappers, including CNN, continue to move more races in the Democrats' direction.

And yet, the Democrats' position on the generic congressional ballot seems to have worsened since the beginning of the year. Just this month, four "gold standard" pollsters (i.e., live interview surveys that call cell-phones and are transparent about their data) show an average lead for the Democrats of just five percentage points on the generic congressional ballot. That's down considerably from 14 points in December among gold standard polls.

So what is going on, and should Democrats be worried?

There certainly has been a decline in the Democratic position since the end of last year, though it's not entirely clear that the changing numbers should shift our perceptions of what will occur in November.

The Democratic lead on the generic congressional ballot in gold standard polling over the last two months is among the worst it has been this cycle. They were up by just five points this month. In March, Democrats were ahead by seven points in seven gold standard polls. Before that, there hadn't been two consecutive months when Democrats held a generic congressional ballot lead in gold standard polling of seven points or less since March and April 2017. That suggests that what we're seeing is real movement and not statistical noise.

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