Blueprint static folder with dynamic url prefix

app.py

from flask import Blueprint, Flask, g, url_for

app = Flask(__name__)

elections = Blueprint("elections", __name__)
elec_bp = Blueprint("elec", __name__, static_folder='static')


@elec_bp.url_value_preprocessor
def pull_election_id(endpoint, values):
    g.election_id = values.pop('election_id')


@elec_bp.url_defaults
def add_election_id(endpoint, values):
    values.setdefault('election_id', g.election_id)


@elec_bp.route("/")
def test():
    ## Returns "/elec/1/static/index.js"
    ## To access election_id in route, use g.election_d
    return url_for(".static", filename="index.js")


@elec_bp.route("/question/<int:question_id>/")
def question(question_id):
    ## Returns "/elec/1/static/index.js"
    return url_for(".static", filename="index.js")


elections.register_blueprint(elec_bp, url_prefix="/<int:election_id>")
app.register_blueprint(elections, url_prefix="/elec")