When you look at the relatively small number of statewide 2016 polls, you find that Clinton runs ahead of Republicans by double digits in the three electoral-vote-rich states of Florida (29 electoral votes), Ohio (18) and Pennsylvania (20), each of which voted only narrowly for Obama in 2012.
One reason for this might be that she is running stronger among older voters, since these states have relatively large elderly populations. These numbers suggest Clinton might carry these states by wider margins.
That would be a nightmare for Republicans if voters continue, as they have increasingly in recent elections, to vote straight tickets. That's because Republicans currently hold 17 House seats in Florida, 12 in Ohio and 13 in Pennsylvania.
Many of those Republicans might be in jeopardy if Clinton should turn out to lead down-ballot Democrats to victory. Democrats currently need to net only 17 seats for a House majority.
In addition, it seems likely that Clinton would run stronger than Obama in the Jacksonian belt stretching from West Virginia southwest to Bill Clinton's native Arkansas. That could also put in jeopardy some House seats that look pretty safe right now.
Then there are the Senate contests. The 2016 lineup, with many incumbents elected in the heavily Republican year of 2010, has many plausible targets for Democrats. Even if Republicans win a Senate majority this year, they could lose it in 2016.
You don't have to agree with Democratic analyst Brent Budowsky's suggestion that Hillary Clinton could win 45 states (Bill Clinton never won more than 32) to see the potential: a Democratic president, Democratic Senate and Democratic House.
Republicans' hopes of repealing and replacing Obamacare would be permanently dashed. The left wing of the Democratic Party could push farther than it has dared under Obama.
None of this is inevitable, of course. Hillary Clinton could get roughed up in the primaries and her record as secretary of state could be more a liability than an asset. The Republican nominee could easily run better than Republicans run now. Events could change attitudes.
I think this scenario is unlikely. But it's one plausible extrapolation from current polling.