Poll: Hillary crushes Democratic rivals. Republicans, not so much.

The Hillary Clinton juggernaut is up and rolling toward the 2016 Democratic presidential nomination – and it's even stronger than in 2008, at least in Iowa and New Hampshire, polls show. But the general election is another story.

There’s a new poll out Thursday that helps clarify Hillary Rodham Clinton’s actual standing among 2016 presidential hopefuls.

The NBC/Marist survey covers only two states – but those are Iowa and New Hampshire, which set the early tone in races for the White House. What it finds is that Mrs. Clinton may be unbeatable among Democrats if she declares her candidacy.

She crushes possible intraparty rivals in head-to-head matchups. Overall, her favorability among Democratic voters is 89 percent positive, 6 percent negative in Iowa, and 94 percent to 4 percent in New Hampshire.

That supposed space on her left for a liberal challenger, such as Sen. Elizabeth Warren of Massachusetts? It’s not there in Iowa and New Hampshire. It’s not really there in national polls either – the RealClearPolitics rolling average of major polls has Clinton as the first choice of 65 percent of Democrats in a multicandidate field. VP Joe Biden gets about 12 percent, and Elizabeth Warren, 7 percent.

That’s probably something liberals don’t want to hear as they kick off their “Netroots Nation” conference in Detroit.

“Democrats are overwhelmingly ready for Hillary Clinton to run for the White House in 2016,” writes NBC’s Mary Murray.

Wait, but Clinton was inevitable once before, right? Wasn’t that the story in 2008 – she was the early juggernaut, until freshman Sen. Barack Obama rode antiwar sentiment to pass her on the left?

Not really. She finished third in the Iowa caucuses in 2008. Right now she’s the choice of 70 percent of Iowa Democrats. Four years ago her state polls never broke out of the 30s.

“Liberal revolt is imminent, really,” tweeted Slate political reporter Dave Weigal on Thursday, sarcastically.

But polling on a general election matchup with individual Republicans reveals a different story.

She’s by no means a juggernaut-in-waiting against the GOP. According to the NBC/Marist survey, she’s tied in Iowa with Sen. Rand Paul of Kentucky, 45 to 45 percent. She’s ahead of New Jersey Gov. Chris Christie by only one point, 44 to 43 percent. (In 2012, President Obama won Iowa by about six percentage points, in case you’re interested in the state’s leaning.)

In New Hampshire, a state of similar partisan makeup, Clinton does a bit better: She leads Senator Paul by three points in the NBC matchup and Governor Christie by five.

National polls, which take into account a much broader partisan map, tend to show Clinton doing a bit better in this context. A national Quinnipiac survey from earlier this month put the ex-secretary of State nine points up on Paul, for instance, and nine points up on Christie.

But the general point remains.

“While Clinton looks like an unbeatable juggernaut in the Democratic presidential race if she runs, she appears more vulnerable in a general-election context,” NBC’s Ms. Murray writes Thursday.