Democrats are releasing way more polls than Republicans. Here's what that could mean.

(CNN)First things first: The theme song of the week is ABC Monday Night Football MIKE theme by Edd Kalehoff.

Polls of the week: Four internal House polls released this week by groups aligned with Democratic or liberal causes. Conservative and Republican groups released no internal House polls this week. This is part of a pattern seen this year with left-wing groups putting out 93% of the partisan polls collected by FiveThirtyEight compared to only 7% by right-wing groups.
What's the big idea: The House of Representatives is difficult to predict because non-partisan polling for individual districts is limited and often not that accurate. Much of the polling released is done by partisan groups.
The obvious problem with partisan-sponsored polls is that it tends to only see the light of day when it looks good for the side who is conducting the poll.
    But, of course, a group first needs to get a poll with good results for their side to actually release it. This got me thinking that if one side fields a lot of polls that end up favorable to their side, then maybe they're more likely to release more internal polls than other side.
    It turns out that this has been true in past years.
    Earlier this year, I collected House district level polling since 2006. For each campaign cycle from 2006-2016, I looked at what percentage of House internal polls were put out by left-wing groups compared to right-wing groups and compared it to the election result.
    In every year but one, left-wing groups have put out more internal polls relative to right-wing groups. Still, there is a clear relationship between how many internal polls each side is releasing and the election results. The more internal polls put out by left-wing groups relative to right-wing groups, the better Democrats tend to do in House elections.
    For example, 2006 was the year in which left-wing groups ended up putting out their highest share of internal polls relative to right-wing groups. That cycle, they put out 77% of the internal polls and Democrats had a net gain of 30 House seats in that election.
    Contrast that to 2010, when Republicans had a net gain of 63 seats in the House. That cycle left-wing groups put out just 35% of the internal polls released by either side.
    Of course, we're not close to November yet. Based upon prior election cycles there will be a bit of a reversion to the mean. That is, left-wing groups will probably have a clear edge in polls released come November 2018, but it won't be as large as the 93% to 7% advantage it is today.
    At this point in the 2006 cycle, Democrats had a somewhat similar 85% to 15% lead in percentage of internal polls put out to the public. That declined by the end of the election year.
    Democrats, though, would surely take a 2006-like wave (or something a little bit better). It would be enough to get the net gain of 23 seats to take back the House.
      Now, there is no guarantee that 2018 will look better or even like 2006. We're only dealing with a sample size of six elections here. This year right-wing groups may be withholding good looking internal polls for some unknown reason.
      But count the share of internal polls left-wing groups have put out relative to Republicans as another good sign for Democrats in 2018. Democrats have done very well in special elections, continue to lead on the generic congressional ballot and Republicans have a lot more seats at risk, according to ratings from CNN and others. All of these factors, at this juncture, point to Democrats doing very well in November's House elections.