How, in a region that’s spent decades expressing skepticism about mass transit, do you move forward with plans to roughly double the distance MARTA’s high-capacity service covers?

As one close observer of transit negotiations under the Gold Dome told me this past week, it’s the same way you go about eating an elephant: one bite at a time.

For some reason, transit advocates seem surprised at the failure, so far, of a bid to raise sales taxes by millions of dollars per year to expand rail and bus rapid transit within Fulton and DeKalb counties. Color me more surprised we’ve come as close to that this year as we have.

This is, after all, the year after lawmakers approved nearly $1 billion in additional, annual transportation funding. Yes, that money is earmarked for roads and bridges, not trains and buses. But dollars are dollars, and even amid low gas prices many lawmakers are wary of the blowback from their constituents for raising the fuel levy (among other taxes).

Keep in mind as well that, although Republicans hold more than two-thirds of the seats in the state Senate and nearly as many in the House, relatively few of them represent Atlanta and its suburbs. Less than one-third of GOP legislators hail from the 10-county metro region, only about a quarter from the five counties in the original MARTA act, just 8 percent from the three counties that have joined. The vast majority of GOP caucus members have to be convinced, or to convince their constituents, that MARTA merits more money.

And even among Republicans who do represent those five counties, or just Fulton and DeKalb, there’s a great deal of disagreement as to the best way to pay for transit expansion. There’s the bus vs. rail debate, the county-by-county vs. regional transit debate, the debate between using broad-based taxes versus revenues drawn from the areas through which the rail or BRT routes would actually pass. Some dissenters may be cynically trying to block transit expansion without appearing to be obstinate, but not all of them are.

But despite all that, much of the friction in this year’s MARTA debate comes down to this: Must all of Fulton and DeKalb move together, in the same way at the same time? Why can’t some move ahead sooner than others?

Remember the elephant. One bite at a time.

If Atlanta is ready to proceed with transit on the Beltline or along the Clifton Corridor toward the Emory University area, let it do so. (I’d hold back on most if not all of the Atlanta Streetcar’s plans, though, which I’m not convinced are ready for prime-time. And don’t discount the political damage done by the troubles incurred in the initial phase of the streetcar, as some transit advocates I know feared when plans for it were first announced.) When DeKalb is ready to move on its share of the Clifton line or the line out to Lithonia, let it do so.

But if MARTA and some lawmakers insist on dragging the rest of Fulton along now kicking and screaming, particularly the mayors of north Fulton cities, who are most at odds about how to proceed, they risk sinking the whole effort. Their insistence on this for so much of the session may have already done so.

Time is running out, but never say never until Sine Die. If there’s a way to let some local governments go ahead while others work things out among themselves, take it.