I also live in a Democratic Party controlled District, however, The elected Sheriff and DA are not only Republicans, but Oath Keepers.
Joining the GOP afforded me a committee seat because Republicans are ashamed to be Republicans. Ron Paul, Rand, and many of us remain in the GOP. We may have lost the nomination due to fraud, but this only makes us more destrmined to end the fraud by occupying the GOP and making it a party to be proud of again.
So first, you join the GOP. And many posters below have given you spot on advice about showing up to everything. This is not inexpensive, as partys, funraisers, participation in conventions, everything you've done as grassroots you can do with and in the GOP, and one way or another, you have to afford to go.. begin campaigning immediately, showing enthusiasm, willingness to sign loyalty oaths, chair sub committees, run for offices in the GOP, which offers classes, seminars, events for training one how to fundraise, campaign, lobby, (this can be for free, part of a convention or an event I've seen $350.00 charged.
Be generous with donations to organization you want support.. tea party, religious right, Chamber, local organizations, fire, police, education..
Show up to board meetings, city council meetings, party committee meetings and observe the rolls, learn who is who, learn who is doing what city, county, state, and make some feild trips to state capital, county clerk, city hall, visit facilities and find the person you want to replace. Somewhere in there is the "dream" possition.. I discovered that the elected job I would like the most is Board of Supervisiors, and I believe I can best the newly elected candidate. Thing is, I would have never known that it is a political position I would have considered until I began showing up and observing who is who and what is going on. You will make friends and find alloes and maybe this is the best part.
Especially being a Republican, because being a RepubliCAN at this time in our political history is taking on a mantal of shame one did not earn. It's heroic attempt.. because the majority of people are seduced and under the influence of MSM, they react to the word "Republican", some violently.. and you have to be able to speak up, "I'm a Republican." Which is shocking, even to Republicans. How can you deface yourself by revealing you belong to the party of shame? Because someone has to clean it up, and you need help.. are you willing to help?
I intend to have a GOP entry in the local parades.. I want to have a Restore America float, pass out monopoly money with end the fed message, have a anti-drone drill for peace, and have a NO UN yes, Constituion theme.. think that might wake some folks up? Folks talk about that.. and if it get's in the paper.. we're on our way to changing the hearts and monds of people about government's role, and what our part is.
GOOD LUCK and have fun with it!